High dynamic range

About: High dynamic range is a research topic. Over the lifetime, 4280 publications have been published within this topic receiving 76293 citations. The topic is also known as: HDR.

Digital optical imaging system and imaging method thereof

Abstract: The invention relates to a digital optical imaging system as well as an imaging method thereof. The system is composed of an optical imaging lens group, a DMD micro-mirror array, a CCD image sensor, an exposure time controller, a digital image processor and a controller. The imaging method comprises: making all active pixels in the MD micro-mirror array be in an open state to obtain the pre-imaging of an object being shot, dividing a plurality of regions according to different actual luminance brightness levels after image processing, confirming corresponding exposure parameters required by each region, controlling the time for making the active pixels be in the open or closed state, and shooting and imaging the object being shot again to obtain clear and high-quality digital images. The invention provides the digital optical imaging system and the imaging method for carrying out the random subdivision and multi-step exposal to the object being shot, high quality pictures with high dynamic range can be acquired through one exposure, and the invention is particularly used for shooting and imaging the object being shot with obvious difference of luminance brightness.

Accurate phase measurements of broadband Multitone signals using a specific configuration of a Large Signal Network Analyzer

Abstract: Accurate measurements of time domain waveforms at microwave frequencies are performed using the harmonic sampling principle[1]. This principle used in the Large Signal Network Analyzer (LSNA) enables to transform a measured RF spectrum into an IF spectrum which is then digitized by ADCs. Unfortunately in this principle IF spectrum bandwidth is limited to 10MHz due to the need of high dynamic range ADCs (14bits). In this paper, we propose a new method that enables to accurately measure the phase relationships and the amplitudes of the spectral components of broadband microwave signals. Measurements of a 62MHz bandwidth multitone signal at L Band have been performed and are shown. The extension of the proposed method to wider bandwidth is absolutely possible. Furthrmore the application of the proposed technique to other harmonic samplers than those used in the LSNA is also possible.

Blooming filter for multiple exposure high dynamic range image sensors

Abstract: Multiple-exposure high dynamic range image processing may be performed that filters pixel values that are distorted by blooming from nearby saturated pixels. Pixel values that are near saturated pixels may be identified as pixels that may be affected by blooming. The contributions from those pixels may be minimized when producing a final image. Multiple-exposure images may be linearly combined to produce a final high dynamic range image. Pixel values that may be distorted by blooming may be given less weight in the linear combination.

Multi-octave, high dynamic range operation of low-biased modulators by balanced detection

Abstract: An optical link is disclosed that is operated by a balanced detection technique so as to extend its linear dynamic range, yet substantially eliminate even-order harmonic distortion of the modulated signal. The modulator comprises two parallel arranged Mach-Zehnder interferometers that respectively have a steady state DC voltage bias applied so that the operating points of the Mach-Zehnder interferometers are selected to produce two separate modulated signals, one of which is later phase shifted by a phase shift device so as to provide an output that is combined with the other modulated signal in such a manner so as to cause a subtraction, leaving the final output signal substantially free of any unwanted even-order harmonic components in order to provide for a multi-octave response characteristic.

Exposure time estimation for high dynamic range imaging with hand held camera

Abstract: The limited dynamic range of a camera may be extended by composing differently exposed images of the same scene. The nonlinear camera has to be calibrated ra- diometrically first. We show that the calibration process can be difficult for real cameras. The improvement can be achieved if linear 12-bit RAW images are used as of- fered by modern mid-class and professional cameras. The knowledge of exposure time positively affects the radiomet- ric quality of the composed high dynamic range (HDR) im- age. This knowledge also helps in registration of differently exposed hand held shots. This contribution presents a new method for estimating exposure times from the histograms of images captured using a linear response camera or gen- erated from a RAW image. The presented method does not require spatially aligned images. The actual process of HDR image composition needs perfectly aligned images on its in- put. We present a method for registering differently exposed images captured with a hand held camera. The presented registration method enables capture of HDR images without the need of mounting a camera on the tripod. The methods are implemented in Matlab and tested on real data.